Here are the top 5 words and phrases that caused the most confusion while I was living in Ireland. These generally apply to England and Scotland as well.
5. Jelly vs Jam
In the US 'jelly' refers to the fruit preserve that is spread on toast at breakfast or eaten with peanut butter in a sandwich.
In Ireland, 'jelly' is gelatin: boiled skin, bones, and connective tissue of animals used in foods such as Jello.
This is why Europeans who have not had a Peanut-Butter and Jelly sandwich find the idea utterly revolting.
4. To Go vs Take away
The phrase 'To Go' will be met with blank stares in fast food restaurants. The key phrase to get your meal to go is 'Take away.' This wasn't to hard to figure out since most places have signs that say 'Take away;' though, this was very important as most of my dinner was take away.
3. Pick up vs Collection
This is subtly different than the 'to go' problem. For some reason, when ordering food by phone ahead of time that I wanted to 'take away' the words 'take away' didn't work if the place offers delivery. In the US we usually say 'for pick up' instead of 'to go' when ordering from a place that delivers, e.g. a pizza, so it's understandable 'take away' doesn't work.
After many different tries I finally hit on the secret code: "I would like to order for collection," and my life became much happier.
2. Next Friday vs This Friday
This one's a lot of fun. In the US, when referring to days of the week 'Next' and 'This' are basically synonymous. For example, if it is Monday and you say "let's meet next Friday" or "let's meet this Friday" you mean the one in four days.
In Ireland if on Monday you say, "let's meet this Friday," you mean the one in four days, however, if you say "let's meet next Friday," you mean the one in eleven days!
So we have 'next' as in the 'next one' vs 'next' as in 'the one following the most immediate one'. If your head is spinning, imagine trying to figure this out in real-time, on the a mobile phone, in a rain-storm .
1. MM/DD/YY vs DD/MM/YY
The number one confusion is the date abbreviation. It's insidious, you're trained from kindergarten to write dates on your papers as Month/Day/Year, e.g 9/1/2005.
Think about how hard it is to get used to writing the new year on your checks every January, it takes a bit of extra thinking. Now multiply that difficult by your age, and you get how hard it is to retrain yourself to view 9/1/2005 as January 9, 2005.
One of my Italian friends was almost four months late to start a graduate program in the US because of this problem.
Honorable mention goes to Fries vs Chips.
We call deep fired potato slices 'Fries' the Irish call them 'Chips' and you get them at a Chipper (or a Chippy in England). So that begs the question what are our 'Potato Chips' called?
Crisps, of course ;-)
Let me know of confusions you've encountered in other countries.